Coast on high alert ahead of severe storms

Weather forecasters have warned heavy rain and flash flooding could hit the Illawarra this evening as severe weather from an ex-tropical cyclone in Queensland moves south.

The Bureau of Meteorology has issued storm and wind warnings for the Hunter, Sydney metropolitan and Illawarra areas today, predicting rainfall of up to 300 millimetres in isolated areas, damaging winds and potential flash flooding throughout much of eastern NSW.

The warning prompted State Emergency Service (SES) Illawarra region controller Greg Murphy to cut short his trip to Taree to assist northern NSW crews and return home. He said Illawarra crews were on standby.

"At this stage the bureau's best prediction is that the severe weather may arrive in the Illawarra late [today]," he said.

"We've been advised of rainfall up to 300 millimetres in isolated areas and up to 150 millimetres across large parts of the Illawarra, as well as the possibility of flash flooding and storm damage due to strong winds.

"We also know the North Coast is experiencing high seas with significant swell, which could also extend down the coast to the Illawarra."

Holidaymakers who are set to head home today along the Princes Highway are also warned to drive to the conditions and allow plenty of time for the journey.

Mr Murphy advised residents to tie down any loose objects around their homes, move vehicles away from trees, keep clear of creeks and storm drains and not drive, walk or ride through floods.

In northern NSW, about 500 people have been isolated by floods.

More than 200 calls for assistance were made to NSW SES yesterday as ex-tropical cyclone Oswald moved across the Queensland border.

Winds of up to 140km/h hit parts of the northern rivers, while in the northern NSW town of Darkwood on the Bellinger River, about 500 people are believed to be cut off.

But while residents have been told to stock up, SES spokeswoman Jessica Chan said there were no fears for their safety.

"The community is quite used to it," she said.

While 53 swift-water rescue technicians were moved to the north of the state yesterday to bolster local resources, Ms Chan said the SES would also be focusing its efforts south today as Oswald moved south.

"We expect conditions in the north to ease after lunchtime [today].

"We are expecting heavy rainfall and flash flooding."

A severe weather warning was issued for much of the state, with the Bureau of Meteorology warning that gusts of 100km/h were forecast for the mid North Coast, the Northern Tablelands, the metropolitan and Hunter today.